With the development of terminal technology, portable devices for personal computations are more and more popular, such as pads, portable displays or the like. These light personal computing devices all use rechargeable batteries to supply electricity for a certain period of time. However, limited by its volume, the provided rechargeable battery cannot provide sufficient electric power to meet the power needs in a portable state. For example, for a portable display, when the battery of its own is out of power and the user cannot recharge the portable display in time, it is obvious that the portable display cannot work, thereby losing the meaning of portable.
At present, although there are typical scenes where two portable devices are connected (for example, a notebook is connected to as mobile phone and the two can exchange data), when the notebook is working, it cannot acquire the state information of the battery of the mobile phone. Moreover, it cannot select its own charging circuit to charge the mobile phone or to charge both of its own battery and the battery of the mobile phone at the same time on the basis of the state information of its own battery and state information of the battery of the mobile phone. When the notebook's own battery is in the low battery status, the notebook cannot control the battery of the mobile phone to supply electricity for the notebook either.
Based on this, during the process of the research and practice of the prior art, the inventor of the present invention has found that by means of the prior implementation, after two portable devices are connected, the processing unit of one of the portable dives cannot acquire the status information of the batteries of the two portable devices, so it cannot control which battery should be charged or whether the both two batteries should be changed simultaneously by the charging circuit; similarly, the processing unit cannot flexibly control which one of the two batteries should supply electricity for the portable devices.